NIST WATT BALANCE LIVES.A NIST (National Institute of Standards & Technology, Washington, DC, www.nist.gov) The standards-defining agency of the U.S. government, formerly the National Bureau of Standards. It is one of three agencies that fall under the Technology Administration (www.technology. research team has reassembled the NIST watt balance The watt balance is an experimental electromechanical apparatus that may one day serve as the delineation of an electronic-based definition of the kilogram. The watt balance is a more accurate version of the ampere balance, in which the force between two current-carrying experiment inside its newly decorated home and the reborn apparatus is showing the first signs of life. The upgraded facility includes vibration isolation Vibration isolation is the process of isolating an object, such as a piece of equipment, from the source of vibrations. Despite construction distinctions the essence of all vibration isolation systems are similar. , rf shielding A material that prohibits electromagnetic radiation from penetrating it. Computers and electronic devices used in the home must meet U.S. government standards for electromagnetic interference. , and, perhaps most importantly, a unique vacuum chamber made of fiberglass where the balance resides. The vacuum system vacuum system Urology A mechanical system used to facilitate and maintain an erection; an erection erector. Cf Penile implant. has successfully achieved a pressure which is sufficiently low to virtually eliminate the largest uncertainty component in the previous version of the experiment. Heat dissipation of the main measurement coil and breakdown of the electrostatic actuators at this pressure have been investigated and do not pose a problem as initially feared. Recently the researchers made some preliminary measurements, balancing the force of a 12 g mass in local gravity against an electromagnetic force produced by the auxiliary feedback coil and magnet. Best scatter to date is 5 X [10.sup.-5] g over a 3 minute measurement which translates to 5 x [10.sup.-8] of the 1 kg standard used in the experiment. Although just the first steps toward the ultimate goal of monitoring the drift of the artifact mass standard in terms of highly stable electrical units, these early results are very encouraging. |
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